Hydrocarbon conversion process



United States Patent r 3,255,209 HYDROCARBON CONVERSION PROCESS Morris Teplitz, Lawrence, Kans, assignor to The Kansas University Endowment Association, Lawrence, Kans., a non-profit corporation of Kansas N0 Drawing. Filed Sept. 5, 1961, Ser. No. 135,731 2 Claims. (Cl. 260329) This invention relates to a new and useful chemical conversion process. In one aspect, this invention relates to a process for the manufacture of aromatic derivatives and sulfur-containing hydrocarbons. In another aspect, this invention relates to a method for the conversion of aromatic hydrocarbons to other aromatic hydrocarbons and aromatic thiophenes.

Aromatic compounds are useful in the preparation of various other chemical compounds, such as acids. As is well-known in the art, aromatic compounds are useful as intermediate compounds in the manufacture of various dyes, explosives, pharmaceuticals and other chemicals. Production of aromatics and aromatic thiophenes by isolation from coal tar and by synthetic methods is relatively expensive and is characterized by low yields and low selectivity or purity of the desired product. It is much to be desired, therefore, to provide a more direct process and a less expensive process to produce aromatic derivatives.

It is an object of this invention to provide a new and useful process for the production of aromatic hydrocarbons and aromatic thiophenes.

It is another object of this invention to provide an improved process of increased yield for production of aromatic derivatives from alkyl aromatics.

It is still another object of this invention to provide a process for the production of aromatic thiophenes.

Various other objects and advantages of the present invention will become apparent to those skilled in the art from the accompanying description and disclosure.

According to this invention, alkyl aromatics are converted to aromatic derivatives in the presence of an oxide of sulfur and a dehydrogenation and cyclization catalyst. The products produced depend upon the starting alkyl aromatic for the process. In some instances the nonsubstituted aromatic compounds, such as naphthalene, anthracene and phenanthrene, are produced. In other instances substituted aromatic compounds, substituted with a heterocyclic ring or a fused heterocyclic ring, are produced, such as the arylthiophenes.

The alkyl radical of the alkyl aromatic starting material has a linear chain of at least 2 carbon atoms, preferably of at least 4 carbon atoms. Both primary and secondary alkyl aromatics may be utilized as the starting material. The product with either the primary or secondary alkyl aromatic starting material will be the non-substituted aromatic derivative, except when the maximum number of carbon atoms vicinal to the alpha-carbon atom is two, the product contains a heterocyclic ring, such as an aryl thiophene. In other words when the number of carbon atoms vicinal to the alpha-carbon atom of the alkyl radical is greater than two, the product is the result of arcmat-ization and the heterocyclic ring is not produced.

For example, the conversion of normal butyl benzene in the presence of an oxide of sulfur and a conventional dehydrogenation-cycylization catalyst will yield naphthalene in accordance with the following (unbalanced) equation;

"ice

In the case of ethyl benzene or secondary butyl benzene, the product is 3-phenyl thiophene or benzothiophene, respectively, in accordance with the following (unbalanced) equations:

phenanthrene anthracene I Y O 0 A1 1 rcata yst (l-Qd so. l 1 500 0. f O C H [I H II C C C C S S 4 Cr-Al catalyst f -i- S02 H C C S 0 oo-o (7) C CTC C Cr-Al catalyst anthracene phenanthrene Conversion of the alkyl aromatic hydrocarbons to other aromatic hydrocarbons and to thiophenes by the process of our invention is accomplished, as previously stated, in the presence of a conventional dehydrogenation and cyclization catalyst. Examples of some catalysts which can be used to carry on the process of the invention are activated carbon; activated alumina; bauxite; fullers earth, particularly attapulgite; silica gel, bentonite; synthetic silicates; supported platinum catalysts, such as platinized asbestos, platinized alumina, platinized carbon; metals, such as platinum, palladium, nickel and copper; molybdenum oxide; chromium oxide; tungsten oxide; titanium oxide; vanadium oxide; cerium oxide; thorium oxide; nickel sulfide; tungsten sulfide; or any of a number of oxides or sulfides of the metals of groups IV, V, VI, VII and VIII of the Periodic Table. Mixtures of catalytic elements can be used, if desired, without departing from the scope of this invention. The catalysts can be used alone or in supported form on either inert or active carriers, and contact can be had with the catalyst in a fixed bed, in a moving bed or in a fluidized state, as desired. Suitable supports for the catalytic material include alumina, alumina gel, bentonite, charcoal, silica and silica gel. When used on supports, the catalytic elements are present in an amount between about 1 and about 25 weight percent. Chromiacontaining activated alumina and molybdenum oxide-containing activated alumina catalysts have been found to give excellent results. After use, catalysts may be regenerated, if necessary, in conventional manner by burning in air, oxygen and/ or steam to remove carbon deposits, sulfur, if any, etc. Sulfur deposit has been found to poison the catalysts drastically and should be avoided. Potassium carbonate treatment of the catalysts may prolong their life, but may result in some decrease in activity.

The supported catalysts are prepared in a conventional manner. For example, to the supports, either in powdered or granular form, are added various compounds of the preferred catalytic elements, either by impregnating the granular support with a solution of a salt of a volatile acid and then it is dehydrated and calcined to leave an oxide residue, or hydroxides may be precipitated onto the granules of support by suspending them in solutions of salts and adding alkaline precipitants after which the suspended material consisting of refractory supports and adhering hydroxide is again dehydrated and calcined to leave a residue of catalytic oxide on the surface and in the pores of the support. The preparation of catalysts for use in the process of this invention is not limited to the use of any particular method of adding the catalytic compounds or elements to supports, and any method suited to the deposition of the particular element chosen may be employed. If desired, a powdered and refractory support may be impregnated with a suitable compound and the composite formed into particles by extrusion or pelleting methods before or after calcination.

Not all of the compounds, particularly the oxides of the preferred catalytic elements, have the same or exactly equivalent catalytic value in accelerating the reactions involved in the invention, and when different oxides are used on different supports, optimum conditions for the formation of maximum yields of the desired compounds will vary.

+ S O i Cr-Al catalySi;

The oxide of sulfur used to carry out the process of the present invention can be in the form of S0 S0 or mixtures thereof. The oxides of sulfur can be added to the aromatic hydrocarbons to be converted or directly to the zone in which conversion takes place, or may be formed in situ in the conversion zone. To form the oxide of sulfur in situ in the conversion zone, sulfur and/ or sulfurcontaining compound, together with added oxygen, are introduced into the conversion zone, by being added separately to the aromatic hydrocarbons to be converted or in the case of the sulfur compound, may be already present in the feed stream. As the added oxygen reactant, pure oxygen, air, or enriched air can be used. Suitable combinations useful in forming sulfur dioxide in situ include sulfur and oxygen, H 8 and oxygen, and sulfides, mercaptans, and other sulfur-containing compounds and oxygen. It has been found economical and preferable to use relatively pure sulfur dioxide which can conveniently and easily be added to the hydrocarbon feed stream. In the case of certain secondary all-:yl aromatic hydrocarbons, as previously discussed, the sulfur combines with the alkyl aromatic starting compound to form the heterothiophenes.

In the process of this invention, the proportion of oxide of sulfur introduced into the conversion zone can vary over a wide range from as low as 0.1 mol to as high as several mols per mol of alkyl aromatic hydrocarbon to be converted, preferably in the range of from about 0.25 to about 4 mols per mol of alkyl aromatic hydrocarbon, more preferably in the range of about 0.3 to about 3 mols per mol of hydrocarbon. The appropriate quantity of sulfur dioxide may be formed in situ during conversion by using an 50 yielding material, or by providing for conversion of sulfur to S0 Hydrogen sulfide may be produced as a product of the process of the invention, and such can be separated from the conversion products and converted to sulfur dioxide for use in further conversion. Also, water is produced. In carrying on the process of this invention, it has been found desirable to avoid excess sulfur dioxide because if an excess of sulfur dioxide exists, hydrogen sulfide formed in the conversion reacts therewith to give sulfur which deposits on the catalyst to poison it. Sulfur dioxide in the conversion effluent should be avoided and appearance of sulfur dioxide in the effluent usually indicates a decrease in catalyst activity, making it advisable to regenerate the catalyst.

In carrying out the process of this invention, a suitable temperature of conversion is maintained in the range of from about 400 C. to about 700 C., preferably in the range of from about 475 C. to about 600 C.

Conversion can be carried on at pressures considerably less than atmospheric down to 1 p.s.i.a. and at relatively high pressures up to 2000 p.s.i.a., and more can be used, if desired. The pressure utilized may depend upon whether vapor phase or liquid phase operations are to be employed. It is preferred to use pressures in the range of atmospheric to p.s.i.a.

In operating the process of the invention, the hydrocarbons to be converted are maintained in contact with the catalyst in the presence of the oxide of sulfur for a suitable length of time to give the desired conversion, preferably from 0.3 to 20 seconds, more preferably a time in the range of from 0.6 to 6 seconds. However, since quantity of catalyst in relation to the feed as well as the contact time is important, both of these features may be expressed as space velocity. Thus, it is preferred to use feed rate of between about 0.2 and about 10 v./hr./v. (volumes of liquid hydrocarbon feed per hour per volume of catalyst in the conversion zone).

Operational procedures in carrying on the process of the invention can be any of the conventional mixing, contacting, separation and recycling methods which are suitable for vapor or liquid phase conversion of the alkyl aromatic hydrocarbons to the desired products. It may be desirable to preheat the feed hydrocarbons to be converted,

and the oxide of sulfur prior to contact with the catalyst. The oxide of sulfur can be added to the feed stream prior to preheat or after the preheating step. The process of this invention is exothermic, and such should be taken into account in determining the degree of preheat. For example, preheating to within 25 C. to 75 C. of the desired conversion temperature for the conversion has been found to work well, allowing for adequate control of conversion temperature.

The dehydrogenation and cyclizing catalyst used in the process of this invention can be employed in a fixed bed, or a moving bed with continuous catalyst regeneration associated therewith, if desired, or the catalyst can be employed in fluidized form, with continuous regeneration associated therewith, if desired. Burning to remove deposits of carbonaceous material and sulfur, as previously mentioned, may be desirable. Steam to control regeneration temperature during burning may be used.

The common and usual separation means can be used to separate and remove desired products of the process of this invention, such as fractional distillation operations, selective adsorption processes employing activated charcoal, silica gel, etc., or selective absorption processes, using for example, 'cuprous salts. If desired, one can employ liquid-liquid absorption separation processes, or liquid-gas absorption separation processes to separate the reaction efliuent and recover desired constituents thereof. Water produced by the process of this invention can be separated from the hydrocarbons by condensation and decantation.

The following examples are offered as a better understanding of the invention and are not to be construed as unnecessarily limiting thereto.

Example I The run described in this example relates to the conversion of sec butyl benzene. Sec-butyl benzene is pumped through a conventional preheat section to vaporize the feed and downward through a fixed bed of granular catalyst (Harshaw Chrome-Alumina Cr-0102 T, Aa-inch in diameter) at a liquid hourly space velocity of from about 0.8 to about 1.0. The catalyst bed temperature ranged from about 500 C. to about 550 C. Sulfur dioxide was charged to the reactor continuously with the hydrocarbon feed (sec-butyl benzene) at a mol ratio of SO /hydrocarbon of 0.9. Initially, the hydrocarbon feed was introduced first and the sulfur dioxide was not introduce-d until hydrocarbon appeared in a conventional receiver at the outlet of the reactor. This sequence of charge was important. If sulfur dioxide had been introduced first, the catalyst would have been rapidly fouled or poisoned. The conversion in this reaction was so high that the efiiuent from the reactor solidified in the vapor conduit leading to the receiver, and, therefore, it was necessary to This run with n-butyl benzene was run under essentially similar conditions as in Example I. The liquid hourly space velocity was about 1.0; the temperature of the catalyst bed was about 500 C. to 540 C., and the SO /hydrocarbon feed mol ratio was about 1.0. Product recovery was about based on hydrocarbon charged. The product collected in the receiver from this reaction contained about 30% liquid, mostly unconverted n-butyl benzene, and about 70% crystalline solids. These solids were a mixture of a major proportion of napthalene and a minor proportion of 2-phenyl thiophene. In general, the ratio of naphthalene to 2-phenyl thiophene in the reaction product can be controlled to some extent by controlling the operating conditions for the reaction; higher operating temperatures favor the formation of the thiophene compound; also, higher SO /hydrocarbon ratios appear to push the reaction in the directionof increased thiophene formation. Without sulfur dioxide as a co-reactant, little, if any, naphthalene was produced.

Example III This Example, carried out similarly to Example I relates to a run with n-butyl naphthalene; actually the feed appeared to be a mixture of alpha-butyl and betabutyl naphthalene. The liquid hourly space velocity for the reaction was about 0.7, the temperature of the catalyst bed was about 500 C. to about 520 C., and the 80 hydrocarbon feed mol ratio was about 1.7. Product recovery was about 80% based on hydrocarbon charged, and the product contained about 80% phenanthrene. X-ray diffraction indicated there may have been a small amount of anthracene present. Some phenanthrene could have been formed without the addition of sulfur dioxide, but the addition of sulfur dioxide materially increased the yield of phenanthrene.

Example IV This was made with di-n-butyl benzene in a manner similar to Example I. The liquid hourly space velocity was about 0.7, the catalyst temperature was about 500 C. to 515 C., and the sO /hydrocarbon feed mol ratio was about 1.3. A crystalline product was obtained which was identified as anthracene.

Various modifications of the reaction conditions and the use of various hydrocarbon feed compositions may become apparent to those skilled in the art without departing from the scope of this invention.

Having described my invention, I claim:

1. The process for the conversion of an alkyl aromatic hydrocarbon which comprises reacting an alkyl aromatic hydrocarbon containing an alkyl radical having at least 4 carbon atoms and in which the number of carbon atoms vicinal to the alpha carbon atom in either direction is a maximum of 2 with sulfur dioxide in the presence of a dehydrogenation and cyclization catalyst at a temperature between about 400 and about 700 C. to produce an aromatic thiophene.

2. The process of claim 1 in which said alkyl aromatic hydrocarbon is sec-butyl benzene and said aromatic thiophene produced is 3-phenyl thiophene.

References Cited by the Examiner UNITED STATES PATENTS 2,557,678 6/1951 Neuhaus et al. 26330.5 2,691,040 10/1954 Bloch et al. 260-329 OTHER REFERENCES Hartough: Thiophene and Its Derivatives, Interscience Publishers, Inc., New York, New York, 1952, pages.

WALTER A. MODANCE, Primary Examiner.

DUVAL T. MCOUTCHEON, Examiner.

J. T. MILLER, J. A. PA'ITEN, Assistant Examiners. 

1. THE PROCESS FOR THE CONVERSION OF AN ALKYL AROMATIC HYDROCARBON WHICH COMPRISES REACTING AN ALKYL AROMATIC HYDROCARBON CONTAINING AN ALKYL RADICAL HAVING AT LEAST 4 CARBON ATOMS AND IN WHICH THE NUMBER OF CARBON ATOMS VICINAL TO THE ALPHA CARBON ATOM IN EITHER DIRECTION IS A MAXIMUM OF 2 WITH SULFUR DIOXIDE IN THE PRESENCE OF A DEHYDROGENATION AND CYCLIZATION CATALYST AT A TEMPERATURE BETWEEN ABOUT 400* AND ABOUT 700*C. TO PRODUCE AN AROMATIC THIOPHENE. 